Do not remove non-namespaced strings when namespace option is enabled.

If you enable namespaces grunt-angular-translate will remove non-namespaced strings. So it will e.g. include `MODULE.MYTEXT`, but will remove `MYTEXT`.

Actually this seems to be by design, but I think it is nonsense and confusing. it's definitely not what is expected by the user, and actually it can make some sense to have non-namespaced strings for globally available texts.